Gale Warning 254, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
255 PM AKST Thu Nov 16 2017

.SHORT TERM.../ through Saturday night / Current forecast
generally on track. The low is developing in the northern gulf as
expected with the upper level support crossing the Alaska Ranged
and Alaska Peninsula into northwest gulf. The snow for the
northeastern gulf coast should be beginning shortly. The new
solutions of the models have fairly good agreement on the low and
relative humidity features though it may be slowing everything
down between 1 and 3 hours. Lacking any significant key
indicators to suggest changes needed, forecast from late tonight
into Friday evening was unchanged. Will continue to monitor
through the event to adjust as needed.

The responsible low will track southeast and attract a low of the
eastern pacific that is being move northeast and then the two will
begin to interact and rotate about each other. Expect drying
conditions behind the first low from the northwest under a
surface ridge that develops and suppressing the showers. A cold
outflow redevelops for the Lynn Canal region through later
Saturday.

.LONG TERM.../Saturday through Thursday/...A significant winter
weather event will be just winding down at the start of this long
range forecast period. Even as this system clears the area to the
south and east, another developing weather system will be headed
out way. As of yesterday, it looked like this second low and
associated front would approach from the west. Model agreement is
good and are now depicting the low to drop southeast out of the
Bering Sea and cross the southwest interior of the state on
Sunday. The low itself and a majority of the frontal precipitation
will remain out over the gulf through Monday morning and at that
time model agreement diminishes significantly. Current preference
is for the ECMWF, which develops a triple point low on the front
over the eastern gulf and rotates the front north and east over
the panhandle. The Canadian NH is depicting a similar pattern, but
is not as strong with the development of the triple point nor the
associated front. Based on current snow versus rain predictors,
including 1000-8050 mb thickness values, 850 mb temps, 1000-500mb
thickness values, low level wind directions, and, of course
surface temperatures, precipitation from this second system will
at least start out as snow for all locations but the southern
zones 27 and 28. Potential is there for the snow level to retreat
north as far as the Icy Strait corridor by Wednesday morning due
to low level warm air advection from the south, but that is a
long time into the future and a lot can change between now and
then.

&&

.MARINE...With winds subsided after the last few days winds are at
small craft levels or less. Will see a narrow barrier jet band of
winds between Cross Sound and Yakutat Bay late tonight, that will
alter to more of and outflow from Cross sound on Friday. Expect
the outflow winds to redevelop Friday into Saturday

&&

.AVIATION...Expect deteriorating conditions due to snow to develop
tonight and last in Friday that will lower ceilings down to 3000
for less and likely to 1000 to 1500 feet on Friday with lower
visibilities in snow as well. Also as the frontal feature swing
across the southern panhandle on Friday low level wind shear is
also probable south of Frederick Sound.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from midnight tonight to 4 PM AKST
     Friday for AKZ026.
     Winter Weather Advisory from 9 PM this evening to noon AKST
     Friday for AKZ024.
     Winter Storm Warning from midnight tonight to 9 PM AKST Friday
     for AKZ025.
     Winter Storm Warning from 9 PM this evening to noon AKST Friday
     for AKZ022.
     Winter Storm Warning from 9 PM this evening to 4 PM AKST Friday
     for AKZ020-021.
     Winter Weather Advisory from 9 AM to 9 PM AKST Friday for AKZ029.
     Winter Storm Warning from midnight tonight to 4 PM AKST Friday
     for AKZ019.
     Winter Weather Advisory from 6 PM this evening to 6 AM AKST
     Friday for AKZ017.
MARINE...Gale Warning for PKZ013-022-043-051.
     Small Craft Advisory for PKZ011-012-021-031>036-041-042-052-053.

&&

Bezenek/Fritsch

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